Instruction set architecture is distinguished from microarchitecture, which is the detailed description of the system that is sufficient for completely describing the operation of all parts of the computing system, as well as how they are inter-connected and inter-operate to implement the ISA.

Computers with different microarchitectures can share a common instruction set. For example, the IntelPentium and the AMDAthlon implement nearly identical versions of the x86 instruction set, but they are very different in internal designs.